Wave transmission



R. A. HEiSlNG WAVE TRANSMISSION Fild Aug. 17, 1920 2 Sheets-Sheet 2 v ln venTor:

iry.

, To all whom it may concem:

efiect upon another tendsto change in thi Patented May 19, 1925.

UNITED ST RAYMOND .A; Hnrsme, or Ease ORANGE, New JERSEY, AssIeNon. ro wnsrnaN nnnormc comrA Y, mconrona'rnn, on NEW YORK, N. Y., A- CORPORATION or 'NEW Yong.

wavn TRANSMISSION.

Applioation filed August, 1920, Srial'No. 404,258.

Be it known that I, RAYMOND a citizen of the United States, residing at- East Orange, in the county of Essex, State,

of New Jersey, have invented certa-innew and useful Improvements in Wave Transmissions, of which. the following is a full,

clear, concise, and exact description. I

rangements repeaters or equivalentsystems ofvacuum tubes'by alternating current or fluctuating direct current. Anfobject of the invention isto reduce to a minimum the effect of the output circuits of'the tubes. y In carrying out the invention circuit arrangements are provided whereby the dis-- purpose the particular terminals of some of the filaments which are connected to their associated plates and grids'are directly connected to one side of the filament heating circuit and the terminals of other filaments which are directly connected to their associated ids and plates are connected to the other side of the circuit. In another arrangement a. three wire or divided circuit is employed. Some of the vacuum tube filaments are connectedto one side of the divided circuit and some .to the-other side. 'A

' neutral conductor,'whichimay be grounded, is employed. By connecting part of the tubes to one side of the circuit and part to another side the tendency of the alternating currentto introduce undesirable efiects in the system is greatlyreduced.

In general, thisi tendency is to roduc'e a cyclic variation 'n the grid and p ate 1011fcuits corresponding in frequency to the fre- .quency of the alternating-heating current or a multiple thereof This is due to 'the fact that the average 'ment with respect to t s cyclicmanner. The two forms of cirqiitgdescribed herein have the common feature;'otYcounter-acting the effect produced upon'one-tube ;or; group of tubes .by' a substantially equal? andflopposite tube or group of tubes.

7 'more current otential of theftila e grid and cathode Various modified'arrangements of each of these forms of circuits may be.utilized.

iBa'tteries, such as .dry batteries have been frequently and commonly used, heretofore, to polarize the grids of vacuum tubes-with respect to their cathodes,v There are sev:

eral disadvantages in the use of batteries of most batteries is highly variable and is much higher when they are-fully char ed than when they are Wholly or'partially is-' charged. Furthermore, batteries of this kind often become discharged from leakage TES PATENT OFFICE.

for this purpose. The electromotive force This invention relates to improved arfor.heat'ing the filament'ary or Y othercathodes of asy'stem of vacuum tube teries are discharging current their. terminal electro-motlve force 1s very much less than when current is passing therethrough in a. charging direction which often occurs owing to the leakage current which passesin the grid circuit of tubes. Var'iationsof grid potential will result from this action. Thus a with a dry cell battery with whichupon open circuit the electro-motiveforc'e is ten volts, the discharging electro-motivieforce may be only seven volts. If such a battery 'is placed in circuit to, negatively polarize the grid of a tube, and"leakage current passes in a reverse direction through the battery the terminal potential diiferencesa across the leak path circu'it rise .to fourteen volts or higher. In order. to. avoid these difliculties it is proposed to employ mechanical generators as sources to apply working potentials to the grids of hr cs. Hereto fore .it has been thoughtv impractical to do this because the fluctuations in the current from such generators would be impressed.

upon the grid. Assmall variations of potential upon the gridofya tube in. general cause a large v'ariationfofzol tput current, an objectionable disturbance results. .One or variationsfin. the direct current supplied from a direct current machine usually have a frequency-within the of'andition'. Hence the variations are range 7' especially undesirable in 'modulating systems for. use in the radiation of electromagnetic waves of considerable'power. It is proposed toutilize a filter for eliminating the commutator and other noise producing I variations from the id circuit. I A aim 1e filter if properly esigned and -suitaly related to the grid circuit is found-"to func tion efficiently. A lay-pass for allowing the alternating current supplied to the input circuit of thevaouum tube to ass around the generator circuit is provide This bypass may comprise "one or more of the elements that make up the filter. By making use of a potentiometer in circuit with the 'generatorthe grids of a number of. tubes aving different functions may be polarized from a single machine.

Al precise' adjustment of grid voltage may be securedwhich will remain substantially constant so long as the machine voltage remains constant; Variations iii leakage cur rent through the grid circuit will have little effect upon the system, particularly .iffthe resistance of the grid polarizing machine be made small.

' Other and more specific objects of themvention will be apparent from a perusal of.

the appended claims.

The various features of the invention will be better understood by reference to the following description, taken in connection withthe accompanying drawing, wherein Fig. 1 represents-a multiplex radio system having threetransmitting systems for transmitting three telephone conversations simultaneously by-means of one antenna, a comlete circuit diagram of one of the systems cing shown, the second system being out lined by rectan ular blocks, and the third being merelyind icated; Fig. 1 is a modified form of circuit illustratin the adaptability of a machine generator or polarizing the grids of the vacuum tubes shown in Fig. 1 and constitutes a substitute for that portion of Fig. 1 to the left of the line Y-Y; Fig.

2- is a complete system which may be substituted for anyone-of thethree transmission systems of Fig. 1; Figs. 2" and 2 illustrate alternative forms of the filament heating circuit illustratedin Fig. 2. I

Referringin detail to Fig. 1', the line L represents any circuit such as a telephone line, in which are producedlow frequency signalling waves to be transmitted upon a high frequency carrier wave. The lowfre quency waves are im ressed upon the input circuit of a three-eectrode vacuum tube system V which typifies any variable impedance system. The anode-cathode -circuit of the system V is supplied from the source 1 through a choke coil 2 which is adapted toprevent the passage of current variations having frequencies such .as exist in. line L. Assumingthat the switch it.

x is positioned upon thecontact 3 then there will be connected in parallel with the system V with respect to'the source 1 and coil -2, an oscillation generating system- 0, a

high frequency amplifying system HA and e ciency of the system the system HA than exists HA will not have its a second high frequency amplifying system HA. Each of the'systems V, 0, HA and HA? may consist of a single vacuum tube or eguivalent device or any suitable number of vacuum tubes or equivalently functioning devices arranged in" parallel. The system V may be of any kind which efficiently varies the space current of the remaining tubes of the system; The oscillat- .ingsystemO as illustratedlisof a wellwhile-the capacity 8 allows speech frequency rent'is supplied to the system 0. through requency variations -from pass- I Variations to Pass y.- The function of resistance 7 andcapacity 8 is to cause'the' oscillations generated by the oscillator to be more completely modulated; Since the space current in the sfystem will be varied in accordance wlth low requency variations of lmpedance 1n the system V, the waves enerated by system 0 will be modulated 1n accordance with these low frequency waves.

The modulated waves produced are impressed upon the input circuit of the high frequency amplifying system HA, of which the output circuit is connected to the input circuit of the second amplifying system HA, for further amplification. Assuming that switch a is ositioned oncontact 3, the space current of the system HA will be varied in a similar manner as that of the loo system 0. The amplifying power or efii- HAwiH as a result of this tend to be moderately greaterat those instants when the waves s pplied. to its input circuit are of large amplitude than at those'instants when the wavessuppl'ied to its input circuit are of small amplitude. A

variable amplification of theapplied high frequency will, therefore, result, tending to produce a greater disparity in the amplitude of the Waves in the output circuit of 1n the waves supplied to the input-circuit. The space current'of the system HA will undergo a corresponding variation and the effect of this system upon the waves supplied to its input .circuit will be similar to that of the preceding amplifier. By moving'the switch 8 to. the contact 3' through the coil -2 and hence it will tend'to act as an ordinary amplifier.- The coil 2 constitutes a high inductive impedance for waves of signaling i. e. speech frequencies. Source 1 and coil 2 together form a highly inductive source.

Still other means. are provided wherebythe amplifying system space current supplied the systems HA and HA may be made to function as substantially distortionless or circuit increases and decrease when this.

amplitude decreases, since this charge is at any instant due to the rate of supplyof electrons from the filament combined with the rate of leakage throu h the resistance 9. When the waves of relatively larger amplitude are applied the. supply of electrons to the grid is more rapid, hen'ce when the amplitude of the supplied wave increases,

the successivewaves will cause a large leak age current to flow to the grids 11 as compared to the leakage current flowing when the amplitude is small. Since the amplyfying power of a discharge repeater of this type tends to decrease as the negative charge upon the grid increases, it will be seen that this compensates for the variation in the amplyfying power caused by low frequency variations in the anode cathode potential supplied to the tube. The extent of this compensation may be varied through a wide range by variationsin the capacity .10 and,

the resistance 9. It will also depend upon the particular design of the vacuum tube being used. In some instances it may be desirable toso adjustthe systems HA and HA that modulation of the waves repeated. thereby will be effected. In other instances,

however, it maybe desirable to so adjust the systems that the minimum of such modulation is affected. Even though no modulation is taking place in both of these 'sys-- 'tcms or either ofthem. there are certain 'a'd vantages connected with the supplying of their space current through the choke coil 2. An important one of these advantages is that the total energy consumption in the amplifying systems with a given high frequency energy outputis reduced. The output circuit of system HA is coupled to the antenna system a by inductively related coils 12 and 13.. Coil 12 is located in a path including condenser 14 and inductance 15 which is tuned to the mean frequency enerated by the oscillating system 0. hunt paths 16 and 17 are tuned by means. of inductance and capacity to offer low -im pedance to waves of the frequencies pro-- duced by the oscillating system 0 of transmitters T and T respectively. The energy impressed upon the coil 12 from the sys-' tems T and T is thus short circ'uited through the paths 16 and 17 and is not impressed-to a material extent upon the space current path of the amplifier HA. In this manner, intermo'dulation of the outgoing waves is prevented. The systems T. and T may identical with transmittei-T except for the modification necessary to, reduce other frequencies or they may di 'er from the transmitterT. One of these systems may,

for example, besimilar to that illustrated in Fig. 1 and the other similar to that illustrated in Fig. 2. p It is desirable that the. antenna system -a"begiven several degrees. 50f freedom corresponding to the frequencies of the seve'ral carrier waves mpressed thereon. This is conveniently accomplished inone manner by: tuning the antenna to the shortest wave length to be radiated which we may assume will be that of transmitter T. A

variable capacity 18 inshunt to the aerial ground capacity of the antenna series to tune to the next longerwave lengthavhich we may assume to be that of system' T. A loop-resonant circuit containing inductance 19 and. capacity 20 is included in series with capacity 18 and is tuned to be resonant at the shortest Wave length, thereby offering a high impedance to the current of these Waves. The tuning for the next longer wave length is accomplished by adding a capacity 21 in shunt to the capacity 18 and providing an additional loop resonan'tcircuit consisting of inductance 22 and capacmty23 for reventing the energy of the waves of the intermediate frequency from passingtherethrough. In tuning, o-f course, the reactance-- of the loop resonant circuits for the-waves towhich they are not attuned will be allowed 'for in adjusting the capacities 18 and -21; I v alternating current source 30 is provided to heat the cathodesaof the vacuum.

tubes, The current is supplied through a transformer 31 across t e secondary of which the'filaments of the tubes are ar-.

ranged inparallel. It will be noted, that the terminals of the filaments 32,-. and .33' which are connected to the-grids .ares connected to opposite terminals of the alternating current source. Thus. whenatheitermi nal of thefilament :32 which is" connected to its associated grid, is made positive by the. alternatin current the terminal of the filament 'i 33 w ich is attached 'to its associated grid, .is made negative; The samecondition-is true as re rds the terminals-- of the'two'filaments whichare connected to" their respective anodes. but this is less' important as. theefi'ect produced in the gridf.

circuit :ismuch greater. It will .be seen that the distorting effect produced -in' ..the

amplifying system HA by the alternating current heating source willbe, to a large extent,compensated for by an equal and op'-. "osite efiectproduced in the system HA.

ith' respect to theisystem V and the system O and other similar .combinationsof;

oscillator and variable impedance tubes, it

makes little differences whether their filavantages ofheating the filaments of a number of discharge tubes of a system by alternating current are considerable, provided the disturbances introduced can be reduced to a small value without undue complication of apparatus or the introduction of a large numberlof transformers. In the systems herein described, it willbe noted that only a single-transformer is necessary to connect the alternating current line-with the system of tubes. If the primary of this transformer is electrostatically' shielded from; the secondary, the electro-static separatio'n of the supply line and the radio systenris complete.

Figf'l" illustratesthe application of a mechanical generator for polarizing the grids of one or more vacuum tubes or systems of tubes. Suppose it is desired to utilize a 'mechanical enerator to apply a negative potential to the grids 11 and 11. The generator G is connected in circuit with the potentiometer resistance 3). The positive terminal of this potentiometer is connected to the cathodes of the system V and HA and taps are taken out from the potentiometer to the respective grids. The tap to the grid 11 is through the conductors 32.

r In addition to the steady direct current, the

output of generator G willhave superimposed thereon, fluctuations due to the effect of the commutator segments. In order to reduce the effect of these fluctuations upon the vacuum tube systems, a filter is provided comprising condensers 33 and 34 in shunt to the portion of the potentiometer included in the grid circuit while inductance 35 is in equivalent arrangements several vacuum tubes or systems may be supplied from a common generator G and, the negative -potcntial applied to the grid circuit of each system may be varied independently offthat applied toany of the others. Variations in leakage current through any system will have little ell'ect in changing the voltage impressed upon that system or upon the other systems provided the generator G is a separately excited machine of low resistance. tuations may be very completely eliminated.

In a system of this sort where several groups of tubes have their grid polarizing source in common it is' necessary that the leads from the source of the grids of some of the tubes be of substantial length, as

shown When for this reason, or any other, grid and filament leads of substantial length are used the leads possess sufficient induc tance and capacity: to pick up disturbances due to stray magnetic and electrostatic fields. Where these disturbances are induced from the output circuit sin ing may result. In the present system ?Fig. 1) such disturbances are prevented from reaching the grids by the grid circuit filters and especially by capacities such as the capacities 34 which serve to shunt out disturbing waves picked up by the leads extending to the filament. transformer and the generator G. V

Fig. 2 in general'corresponds to transmitter T in Fig. -1. Inthe following description emphasis will be putupon the features distinguishing the two systems rather than the features common thereto. The

speech or low frequencycurrents existing in the line L, before being impressed upon the 5 Disturbances due to armature flucerator; hence a filter, F is provided 'to re duce fluctuations in the current therefrom.

It will be noted that this current is supplied through-a speech frequency choke coil 2 to high frequency amplifying systems HA and HA" which are arranged in tandem with respect to each other but in parallel with respect to the variable impedance system V. By this means the modulation is entirely offected inthe high frequency amplifying systems. The current to be modulated is supplied by an oscillation generating system 0, receiving its space current directly from the source 1. The current generated by system 0 is amplified by the high frequency amplifying system'HA and impressed upon the input circuit of the system HA, of which the output circuit is connected to the system HA". The output circuit of each of the high frequency amplifying systems preferably contains a circuit tuned byinductance and capacity to be resonant to the same frequency as that produced by the oscillator O.' The resistance 7 and capacity 8which are in circuit with the plate supply of the system HA' function in a manner similar to the correspondingly markedelements in Fig. 1. The resistance 9 and the condenser 10 in the input circuit of the system HA" like- \vir-e function similarly to those correspondtransformer-s may ingly marked "Fig, 1. Biiproperad'ustment the system HAC mayh -made to f circuit with the high frequency amplifying supplied from the alternating source .throughthe transformer 31. The secondary;

systems, A suitable source 37' is provide to polarize the grids of those resistances.

' The filament heating system of Fig. aisof the transformer 31 may be regarded as a source of heating current- Mains 88-and 39 are connected across the terminals of this,

secondary. A'neutral connection 40 is pro j vided to Which'one terminal of each of the filaments is connected. Where a single vacuum tube, as, for example, LA is utilized for to its associated made correspondmgl ne ative.

- point of the secondary of the transformer 31 is essential. If however, the two halves of the systems are seriously unbalanced, it

such a connecag tion' which is illustrated in Figs. 2* and 2 In Fig. 2, a plurality of transformers 31, and 31' have their primary windings con-' nected' in parallel to the source .30. The

have diflerent or similar connected in series performing one function, this may be connected from the neutralAO to one main 39 While this is balanced by the filament of another system, such as that of the system 0 connected between the neutral 40 and themain 38. Thus, for example,'it will be seen that the filaments of the systems 0 and HA are oppositely connected With respect to the neutral lead of heating current s11 ply system. The effect produced in one of 5h systems. tending to modulate current in accordance wtih the alternating heating current will be compensated for to a large extent, at least, by the opposing efi'ect roduced filament rheostats 41,1ndiv1dual to each filament, are provided; No connection from' the neutral conductor 40 to any intermediate may be desirable to provide The mains 38""and 39ers through the secondaries. In order to'save space,-the tube systems ex cept system V are omitted from Fig. 2, The connection of the filamentsof the tubes winding ratios.

unc-

tion entirely asan amplifier was an ampli-' j fier and modulator combined. It will, be noted that no choke coils correspondin to those marked 6 in Fig. 1 are connecte in of theamplifiers which are not equipped with leak-pathi circuit andplacmg ese Y heating the filaments a 'b the action of said heating currentifor. eel

any unbalanced-current a';;conductive. cont w nie iiiid' the nan-1 is similar tothat in Fig.-' 2', -.-T providevfor motion 42- froin 'ithe neutr'aIAO", to -,a...pointf intermediate to {the secondaries is made. The method of; connecting tubes of the restood by ins' ection of Figs. 2, and 2' p Fig.2? di ers from F1 2 in haying. single transformer 31-;su stituted forthe pair of transfoimersm; 31; The neu tral connection"'i2,-, in-JthiscaSe, is made to a ,1

\maining systems will be sufiiciently' undermiddle point .or'gfinterni'ediate point 'on the:

jsecondar -of-the-J ',triin;for-'mer winding.

The fi ament heatingesystemsi of Figs. 1,

2, 2; and 2", are interchangeable and may be used incircuits suchfas, for *Fi .1 1 or Certain ;featuresofthese; lament heating circuits' 'may be usefully-applied to s stems where uni-directional current is i1se for heating the filaments and disturbs ing fluctuationsare presentin-the uni-direcr tional current; By 11 across each side"thereof,,- the influence of an a filaments Izin a three-wire thedisturbing fluctuations will be'i'educed.

The novel featuresbelieved tobe inherent in the invention are defined in the appended claims. 7 What is claimed 1. A system com'pri vacuum tubes having sing t plurality 0f (1 connections wherec rcuit of one tube v the action thereof. upon another tube.

ouree -upon the input 's compensated for by v filaments and input circuits, a source oftagiernatmg current for ,2. A system] comprisingaplurality of I vacuum Ztubes 'havmgjheated ,filamentary cathodes," an alternat' v tubes and'conneetions wherebytheeflect produced b vary-.

ing the pdtential qffagterminalof t e filamentgof one tjlbe' jetF thefagternating ire-- quency is compensated for potential of a; terminal another tube. v

3."A syst on prism s ace" dischargefdevices, e'ac e filamentary cathode and a;

- d, a source of alternating current for causmg a 'flowy of gc'urrent through said cathodes, -grids .being connected tolthat term nal of ts associated filamentpwhich said source" tends .to. make more positive "at a stant whilethe. ethane? 'dj gri 5 1s connected to that terminals-of mentwlich saidi U negative at -"a' corresponding-instant.

A p ralityfo'f waeuum t ther'ein', conheetiens;adapted for the a p11- 2 its associated cation of-'analternatmgelectromotive orce r whereby the disturbing action of said elecgource of filament,

cathodes fan umber of one of said I l Ft'endsm make more tro-motiye force on one-,aet -0 tubes is com- 7 g pensated for by the action thereof upon another set of tubes.

5. A system comprising a plurality of vacuum tubes, cathodes therein, connections adapted for the application of alternating electro-motive .force to said cathodes, and

connections whereby the disturbing action the electron-emitting cathodes of part of I said devices being connected to one branch of said circuit and part to another 'braneh thereof.

7. A system comprising a three-wire heating circuit and a plurality of vacuum tubes having at least two electrodes, one of said electrodes being an electron-emitting cathode, the cathodes of approximately one-half of said tubes being connected between the "neutral branch of said circuit and one side thereof, and the remainder connected between the neutral branch and the other side thereof. 1

8. In combinatlon, a dlscharge device having an anode andan electron-em'ittlng cathode for permitting space discharge current to flow through said device, a source of current of varying amplitude for rendering said cathode active to emit electrons, means actuated in response to variations of said space discharge current, and a second discharge device for opposing-the effect upon said means of variations in the current from said source.

9. The combination of a plurality of vacuum tubes having separate input and output circuits, an alternating current heatingcircuit for the cathodes of said tubes and connections between one of said cathodes and said circuit whereby an effect upon one tube of alternating voltage applied to said cir-- 4 cu-it compensates for an effect thereof upon another tube.

. 10. -A plurality of space discharge devices having common inputv and output circuits, an alternating current filament heating circuit for said devices, and connections whereby the disturbing efl'ect-of potential variations -in said alternating current circuit upon one of said devices is balanced by the efi'ect uponanother thereof. V

11. A system comprising a plurality of vacuum tubes, each having at least two electrodes, an alternating current filament heat- 111g circuit comprising three conductors, one of which is connected so as to be always at a potential. intermediate the other two, part of said filamentsbeing connected between said first conductor and a' second of said source, and a neutral conductors and part ofsaid filaments being connected between said first conductor and the third conductor. a I

12. .A filament heating means for the fila ments of a plurality of three-electrode discharge tubes comprising a source of alternating current, a plurality of main leads connected across the Zterminals of said eonductor for said filaments, each filament ihaving a. terminal COIlIleQtGdtQSfild neutral iconductor and an' opposite terminal connectedto one of the other mainleads respectively.

13. In combination, a plurality of-transformers having their; rimaries -1n parallel, their secondaries serial wire circuit, and"set's--.. ofwacuumtubes confludedin a threenected across eachofathe pairs of conductorsofthe three-wire circuit.

1AA thermionic system comprising a plurality of thermionic repeaters having cathodes, appropriate circuits whereby said repeaters conjointlynfunction to repeateleotrical waves, an alternating current source for ther cathodes 0f said. repeaters, and means fwherebyIthe;- disturbing effect pro duced byrisaidsou'rce upon one of said repeaters is compensated for by the effect pro-" duced upon the other thereof.

.' In bination, a. discharge device do and an electron-emitting catho e f rmitting space discharge current to flow-through said device, a source of current of viirying amplitude for rendering said cathode active to emit electrons, means actuatedz-iniresponse to the flow ofsaid space discharge current, and means comprising a compensating dischar device, having a cathode rendered active by said source of current, for opposing the effect upon said first mentioned means of variations in the current from said source.

16. In combination two space discharge devices having filamentary cathodes, a current source for heating said cathodes, said cathodes being connected in series with said source, plate and gridcircuits for said devices terminating "at a point between the two cathodes.

havin an 17. In-a combination according to claim I 16,'a ground connection for said point.

18. In a combination according to claim 16, an adjustable resistance in series with each cathodefor regulating the heating .1

fluctuations from said enerator from affecting sa1d cathode-gm mput clrcults.

20..A -system in accordance with claim to said devices, leads from said source to' each device, and a .filter connected across the gridecathode circuit of each device adj acent thereto.

22. Ina system of space discharge devices having grids and heated cathodes operating to relay waves of relatively high frequency, wherein, on account of having common sources for a plurality of tubes or for other reasons, relatively long leads connect the grids and cathodes with their respective polarizing and heating current sources, an input impedance element connected to the grid of a space dischar e device and a condenser connected direct y between. the oathode and that terminal of said impedance element remote from said grid.

23. A system comprisinga vacuum tube,

a second-vacuum tube for feeding the first mentioned tube, a" circuit coupling said second tube to the first mentioned tube, a condenser in series in said circuit, a source oi space current for said tubes, connections for supplying space current from said source to said first mentionedtube said connections having low impedance for alternating currents, 'andconnections from said source to the opposite terminals of said condenser, said last mentioned connections including an impedance element of high inductance.

24. An electron discharge system comprising anode means, cathode means, a source .of space current therebetween, *a divided 1 45 alternating current heating circuit, the respective currents in the branches of said heating circuit dilfering from each other in phase, portions of said cathode means being connected across respective divisions of said heating-circuit whereby voltage fluctuations in one of said portions due to the heating currenttend to compensate for similar fluctuations in another of said portlons.

In witness whereof, I hereunto subscribe my name this 11th day "of August A. D.,, 1920.

RAYMOND A. HEISING. 

